Then that 3D effect is lens and ambient light. The reason I love zeiss planars, distagon and voighlander low element lenses on my 35 mm film and digital cameras. I'm guessing you were stopped down to say f/8 or 11 and left the background identifiable to give context. Shooting wide open with fast glass with the bg a wash of color is easy. Try stopping down a 22 element lens and you won't get this effect, depth with subject sharp/bg blurred, instead you get a flat image with no depth, little micro contrast that a low element count lens does produce. The b&w from those low element count lenses, after only contrast, is stunning instead of muddy shadows.